KT-45777: Move classpath diffing to incremental Kotlin compiler (2/2)

as we need access to the lookup tracker to compute classpath changes
more efficiently and reduce the size of the saved classpath snapshot.

The previous commit only changed the files' paths, this
commit actually updates the files' contents.

Note that classpath snapshotting still happens in Gradle artifact
transforms. (However, the previous commit also moved the code for
classpath snapshotting together with the code for classpath diffing as
they are closely related.)

compiler/incremental-compilation-impl/build.gradle.kts

@@ -15,6 +15,7 @@ dependencies {
     api(project(":compiler:cli-js"))
     api(project(":kotlin-build-common"))
     api(project(":daemon-common"))
+    implementation("com.google.code.gson:gson:${rootProject.extra["versions.jar.gson"]}")
     compileOnly(intellijCoreDep()) { includeJars("intellij-core") }
 
     testApi(commonDep("junit:junit"))